Saturday, July 06, 2013

When Does Heat Subside?

Today marks the third straight 90 degree day and yeah, by definition it's a heat wave. Yesterday and today will arguably mark the sunniest and today arguably the warmest of the stretch as we run into the middle 90's.

While thunder chances increase next week the Bermuda High flattens out and shifts south a bit, we'll still be in a broad west-southwesterly flow of air aloft -- enough to keep us near or at 90 through the middle of next week. While any day between Monday and Wednesday could present enough thunder to prevent a 90 degree day from occurring, odds are most of the next five days feature highs in the 90's...perhaps all five.

The question then turns to when the pattern breaks down and we safely avoid 90 for more than a day. Modeling is suggesting that breakdown occurs Thursday into Friday as a trough pushes through the Lakes and into the Northeast, shoving the Bermuda High offshore and allowing a ridge of heat to build across the Plains. A frontal boundary brings a thunder threat for Wednesday night and Thursday as it crosses the region, with lowering humidity and temperatures that top out in the 80's by Friday at the latest.

The "cooldown" isn't anything substantial...it is July and given we're historically in the warmest days to average, cold air doesn't really have much staying power or traction around here. However, 80's will feel better than 90's, and dew points that are closer to 60 than 70 will be a welcome relief around here given the rather muggy temperature and dew point regime we're in as of late.

Unfortunately, the run-up to this regime shift will be thundery...and the potential for more storms exists every afternoon through the first half of next week.